Information display system and vehicle information display system using the same

ABSTRACT

An information display system configured to unidirectionally display an image to inside or outside of a space via a transparent projected member provided in the space includes an image projection apparatus arranged inside the space and configured to generate and project image light by modulating a light flux from a light source, a transparent sheet provided on an inner surface of a display region set on a part of the projected member, and a light direction changing panel configured to change a direction of the image light from the image projection apparatus toward the transparent sheet of the display region, and the transparent sheet includes a retardation plate, an absorption type polarization plate that absorbs a specific polarized wave, and a transparent diffusion sheet material having a light diffusion function, and projects the image light whose direction has been changed by the light direction changing unit to the inside or the outside of the space.

TECHNICAL FIELD

The present invention relates to an information display system capableof displaying an image to inside or outside of a store (space) byreflecting on or transmitting through a transparent member thatpartitions the space such as a show window glass, and further relates toa vehicle information display system capable of displaying an image toinside or outside of an automobile, a train, an aircraft, or the like(hereinafter, collectively referred to as “vehicle”) by projecting imagelight onto a windshield, a rear glass, a side glass, or a combiner ofthe vehicle by using the information display system.

BACKGROUND ART

As this type of information display system, in general, displaying animage by using a transparent or reflection type screen has already beenknown, and for example, according to Patent Document 1 and PatentDocument 2 below, a transparent or reflection type screen provided witha light diffusion layer containing a binder and fine particles hasalready been known.

On the other hand, as to an information display apparatus for use in avehicle and an information display system using the same, a so-calledhead-up display (HUD) apparatus configured to display trafficinformation such as route information and traffic congestion informationand vehicle information such as remaining fuel and cooling watertemperature by projecting image light to form a virtual image on awindshield or a combiner of an automobile has already been known in, forexample, Patent Document 3 below. In this type of information displayapparatus, in general, in order to monitor the image information as avirtual image for the purpose of reducing the movement of the point ofview of a driver, the configuration in which the image displayed on theimage display apparatus is projected onto the point of view of thedriver by using an optical system including a concave mirror (functionof convex lens) has been adopted in many cases.

RELATED ART DOCUMENTS Patent Documents

-   Patent Document 1: Japanese Patent No. 6133522-   Patent Document 2: Japanese Patent No. 6199530-   Patent Document 3: Japanese Unexamined Patent Application    Publication No. 2015-194707

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, in the above-mentioned magnification projection informationdisplay system or apparatus which is the conventional technology,consideration is not given to the improvement of the light utilizationefficiency by efficient delivery of the image light to the observer, andas a result, there is the first problem that it is difficult to reducethe power consumption of the system and the image projection apparatusincluding the light source of the apparatus.

Further, in a vehicle information display apparatus represented by ahead-up display or the like, AR (Augmented-Reality) information which isa virtual image is displayed so as not to obstruct the view outside thevehicle from the driver, but high resolution and high visibility arealso required when displaying information such as a map. Therefore, aliquid crystal display element (liquid crystal display panel) is oftenused because a high-quality image can be easily obtained and it isinexpensive. On the other hand, since a small-sized liquid crystaldisplay element is used in order to reduce the size of the set, theobtained resolution of the projection image is insufficient, and itposes the new second problem that it is not suitable for displaying ahigh-resolution image displayed on a smartphone or the like.

Further, in the conventional vehicle information display apparatus ofthe head-up display type, when the inclination angle of the windshieldis large (close to vertical), since the place where the imagingapparatus is arranged is limited to the space between the steering andthe windshield, the image light from the imaging apparatus is reflectedin the direction in which the light cannot reach the eyes of the driverafter the reflection on the windshield and the system cannot beestablished, so that the third problem that there is the restriction onthe structure of the vehicle in which the apparatus is installed isclarified.

Further, the conventional vehicle information display apparatus of thehead-up display type is not intended to display image information to theoutside of the vehicle. Therefore, when it is desired to display imageinformation to the outside of the vehicle, an image display apparatussuch as a display is mounted inside the vehicle, and the imageinformation is displayed through the glass of the vehicle. However, inthat case, the image display apparatus obstructs the view of the driver,which is not preferable for safe driving.

In Patent Document 1 and Patent Document 2, which are conventionaltechnologies, a reflection type screen or a transparent screen providedwith a light diffusion layer containing a binder and fine particles usedin an information display apparatus is disclosed, but no considerationis given to efficient delivery of image light to an observer, that is,improvement of light utilization efficiency, and there is no teaching onthe application in vehicles and the specific method, form, andconfiguration for that purpose.

The present invention provides the information display system capable ofdisplaying high-resolution image information even on a glass surface ofa show window or the like and capable of significantly reducing thepower consumption in the system and apparatus including the light sourceand the image projection apparatus by improving the light utilizationefficiency by efficient delivery of the image light to the observer, andthe vehicle information display system using the information displaysystem, instead of the conventional information display system andapparatus. Also, the present invention aims to provide the vehicleinformation display system capable of performing the so-calledunidirectional display in which the information can be visuallyconfirmed by the passengers including the driver inside the vehicle butcannot be visually confirmed from the outside of the vehicle or theinformation can be visually confirmed from the outside of the vehiclebut cannot be visually confirmed by the passengers inside the vehiclevia the shield glass including a windshield, a rear glass, and a sideglass of the vehicle, regardless of the inclination angle thereof, inaddition to the reduction of the power consumption by the improvement ofthe light utilization efficiency.

Means for Solving the Problems

In the present invention, in order to achieve the above-mentionedobjects, first, an information display system configured tounidirectionally display an image to inside or outside of a space via atransparent projected member that constitutes the space is provided. Theinformation display system includes an image projection apparatusarranged inside the space and configured to generate and project imagelight by modulating a light flux from a light source, a transparentsheet provided on an inner surface of a display region set in a part ofthe projected member, and a light direction changing unit configured todirect a direction of the image light from the image projectionapparatus to the transparent sheet in the display region, and the imageprojection apparatus includes an image light characteristic convertingunit configured to convert the image light from the light sourceconstituting the image projection apparatus into image light having anarrow diffusion angle and composed of a specific polarizationcomponent.

Also, in the present invention, in order to achieve the above-mentionedobjects, a vehicle information display system configured to displayinformation to inside or outside of a vehicle by using a part of atransparent projected member constituting the vehicle as a displayregion is provided. The vehicle information display system includes animage projection apparatus provided inside the vehicle and configured toproject image light of the information, a transparent sheet provided onan inner surface of the display region set on a part of the projectedmember, and a light direction changing unit configured to change adirection of the image light from the image projection apparatus to thetransparent sheet, and the image projection apparatus includes an imagelight characteristic converting unit for converting the image light fromthe light source constituting the image projection apparatus into imagelight having a narrow diffusion angle and composed of a specificpolarization component.

Effect of the Invention

According to the present invention, it is possible to provide a new andhighly usable information display system capable of displayinghigh-resolution image information even on a glass surface of a showwindow or the like and capable of significantly reducing powerconsumption by the improvement of the light utilization efficiency byefficient delivery of image light to an observer. Further, a vehicleinformation display system capable of significantly reducing powerconsumption is provided by using the information display system, and thevehicle information display system can perform the so-calledunidirectional display in which the information can be visuallyconfirmed by the passengers including the driver inside the vehicle butcannot be visually confirmed from the outside of the vehicle or theinformation can be visually confirmed from the outside of the vehiclebut cannot be visually confirmed by the passengers inside the vehiclevia the shield glass including a windshield, a rear glass, and a sideglass of the vehicle.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a diagram showing an example of an overall configuration of aninformation display system according to an embodiment of the presentinvention;

FIG. 2 is a diagram showing an example of a specific configuration of alight source apparatus constituting an image projection apparatus of theinformation display system;

FIG. 3 is a cross-sectional layout view for describing a configurationand operation of the light source to perform the polarization conversionin the image projection apparatus;

FIG. 4 is a cross-sectional layout view for describing a configurationand operation of the light source to perform the polarization conversionin the image projection apparatus;

FIG. 5 is a diagram showing an example of a configuration of alenticular lens constituting the image projection apparatus of theinformation display system;

FIG. 6 is a diagram including graphs showing image light diffusioncharacteristics of an image display apparatus;

FIG. 7 is a diagram including graphs showing image light diffusioncharacteristics of an image display apparatus;

FIG. 8 is a cross-sectional view for describing the principle of a lightdirection changing panel constituting the image projection apparatus ofthe information display system;

FIG. 9 is a cross-sectional view showing an example of a schematicconfiguration of a protective cover constituting the image projectionapparatus of the information display system;

FIG. 10 is a diagram showing a coordinate system to measure visualcharacteristics of a liquid crystal panel;

FIG. 11 is a diagram showing angular characteristics of luminance(up-down direction) in a general liquid crystal panel;

FIG. 12 is a diagram showing angular characteristics of contrast(up-down direction) in a general liquid crystal panel;

FIG. 13 is a diagram showing angular characteristics of luminance(left-right direction) in a general liquid crystal panel;

FIG. 14 is a diagram showing angular characteristics of contrast(left-right direction) in a general liquid crystal panel;

FIG. 15 is a cross-sectional view showing a configuration example of alight direction restriction panel provided in the image displayapparatus of the information display system;

FIG. 16 is a cross-sectional view showing a configuration of aunidirectional transparent sheet (reflection type) (first example)constituting the image projection apparatus of the information displaysystem;

FIG. 17 is a cross-sectional view showing a configuration of aunidirectional transparent sheet (reflection type) (second example)constituting the image projection apparatus of the information displaysystem;

FIG. 18 is a cross-sectional view showing a configuration of aunidirectional transparent sheet (transmission type) (first example)constituting the image projection apparatus of the information displaysystem;

FIG. 19 is a cross-sectional view showing a configuration of aunidirectional transparent sheet (transmission type) (second example)constituting the image projection apparatus of the information displaysystem;

FIG. 20 is a diagram showing an example in which the information displaysystem is applied to an automobile;

FIG. 21 is a diagram showing an example in which the image displayapparatus of the information display system is installed on a ceilingportion of an automobile serving as a vehicle;

FIG. 22 is a diagram showing places where images are displayed on glassportions of an automobile when the image display apparatus of theinformation display system is installed on a ceiling portion of anautomobile serving as a vehicle;

FIG. 23 is a diagram showing an example in which the image displayapparatus of the information display system is installed on a ceilingportion of an automobile serving as a vehicle;

FIG. 24 is a diagram showing places where images are displayed on glassportions of an automobile when the image display apparatus of theinformation display system is installed on a ceiling portion of anautomobile serving as a vehicle;

FIG. 25 is a diagram showing an example in which the information displaysystem is applied to a bus serving as a vehicle;

FIG. 26 is a diagram showing an example in which the information displaysystem is applied to a train serving as a vehicle;

FIG. 27 is a diagram including a graph showing a wavelength distributionof natural light such as sunlight;

FIG. 28 is a diagram including graphs showing reflectance of glass withrespect to p-polarized light and s-polarized light of natural light suchas sunlight;

FIG. 29 is a diagram showing an example of a specific configuration ofthe vehicle information display system in which the information displaysystem is applied to a vehicle;

FIG. 30 is a diagram showing an example of a more specific configurationof the vehicle information display system in which the informationdisplay system is applied to a vehicle;

FIG. 31 is a diagram showing an example in which the information displaysystem is applied to a vehicle;

FIG. 32 is a diagram showing an example of an arrangement of the vehicleinformation display system configured to display information to a drivervia a windshield of a vehicle;

FIG. 33 is a diagram showing an example of an arrangement of the vehicleinformation display system configured to display information to a driverand an observer on a passenger seat via a windshield of a vehicle;

FIG. 34 is a diagram showing an example in which information isdisplayed to outside of a vehicle via a rear glass of a vehicle;

FIG. 35 is a diagram showing a relationship between a size of a virtualimage obtained by the information display system and a position wherethe virtual image is generated; and

FIG. 36 is a diagram showing an example in which a light directionrestriction panel provided in the image display apparatus of theinformation display system is installed in a vehicle together with theimage display apparatus.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to drawings and the like. Note that the present invention isnot limited to the following descriptions, and various changes andmodifications can be made by a person having ordinary skill in the artwithin the scope of the technical idea disclosed in this specification.In addition, in all the drawings for describing the present invention,components having the same function are denoted by the same referencecharacters, and repetitive description thereof will be omitted in somecases.

<Information Display System>

FIG. 1 shows an overall configuration of an information display systemaccording to an embodiment of the present invention. For example, in astore or the like, a space is partitioned by a show window (alsoreferred to as “window glass”) 220 which is a translucent member such asglass, and according to the information display system of the presentembodiment, it is possible to unidirectionally display an image toinside or outside of the store (space) by reflecting on or transmittingthrough the transparent member. In FIG. 1, the inside of the show window220 (inside the store) is shown as a far side in the depth direction,and the outside thereof (for example, the sidewalk) is shown a nearside.

More specifically, as shown in FIG. 1, though described later in detail,an image display apparatus 48 provided with a light source andconfigured to generate and project image light to be displayed isarranged above the show window 220 which is a transparent member such asglass, and the image light generated by the image display apparatus 48is unidirectionally displayed to inside or outside selectively by thefunction of a light direction changing panel 54 and a transparent sheet(film) 51 attached to the show window 220 also described later indetail. Accordingly, it is possible to display various kinds ofinformation to inside or outside of the show window 220 by using it, andit is possible to remarkably improve the utilization efficiency of theshow window.

Next, FIG. 2 shows a more specific configuration of the above-mentionedinformation display system, and an image display element 52 constitutingthe above-mentioned image display apparatus 48 is composed of arelatively large-sized liquid crystal display panel with a screen sizeof more than 6 inches. Further, in order to perform correction at alevel of causing no problem in practical use by distortion correction,the resolution of the panel is preferably 1280×720 dots or more.

Also, the image display apparatus 48 further includes a light sourceapparatus 101 constituting a light source thereof together with theabove-mentioned liquid crystal display panel 52, and the light sourceapparatus 101 is shown in a developed perspective view together with theabove-mentioned liquid crystal display panel 52 in FIG. 2.

Though described later in detail, as indicated by arrows 30 in FIG. 2,the liquid crystal display panel (element) 52 obtains an illuminationlight flux having characteristics similar to laser light with strongdirectivity (straightness) and polarization plane aligned in onedirection, by the light from the light source apparatus 101 which is abacklight apparatus, and emits the image light modulated in accordancewith an input image signal to the transparent sheet 51 provided on asurface of the window glass 220.

Also, in FIG. 2, the information display system is shown together withthe liquid crystal display panel 52 constituting the image displayapparatus 48. Also, as shown below, it further includes the lightdirection changing panel 54 configured to control the directionalcharacteristics of the light flux emitted from the light sourceapparatus 101 and a narrow-angle diffusion plate (not shown) as needed.Namely, polarization plates are provided on both surfaces of the liquidcrystal display panel 52, and the image light having a specificpolarization is emitted with the light intensity modulated by the imagesignal (see arrows 30 in FIG. 2).

Consequently, a desired image is projected as specific polarized lighthaving high directivity (straightness) toward the window glass 220 viathe light direction changing panel 54, and it is reflected by ortransmits through the transparent sheet 51 provided on the surfacethereof toward the eyes (not shown) of the observer inside or outsidethe store (space). Note that a protective cover (not shown) may beprovided on the surface of the above-mentioned light direction changingpanel 54.

In this embodiment, in order to significantly reduce the powerconsumption by improving the utilization efficiency of the light flux 30emitted from the light source apparatus 101, in the image displayapparatus 48 including the light source apparatus 101 and the liquidcrystal display panel 52, high directivity is given by an opticalcomponent such as a lenticular lens described below to the luminance ofthe image light which is the light from the light source apparatus 101(see arrows 30 in FIG. 2) and is transmitted through or diffused by thetransparent sheet 51 provided on the surface of the window glass 20 asdescribed below. According to this, the image light from the imagedisplay apparatus 48 efficiently reaches an observer inside the showwindow 220 (inside the store) or an observer outside it (for example, ona sidewalk) with high directivity (straightness) like a laser beam, andas a result, a high-quality image can be displayed with high resolutionand the power consumption by the image display apparatus 48 including anLED element 201 serving as a light source can be remarkably reduced.

<Embodiment of Image Display Apparatus>

FIG. 3 shows a specific configuration of the light source apparatus 101described above. In FIG. 3, the liquid crystal display panel 52 and thelight direction changing panel 54 arranged on the image displayapparatus 48 including the light source apparatus 101 in FIG. 2 areshown. The light source apparatus 101 is formed into a case made ofplastic or the like as shown in FIG. 2, and is configured such that theLED element 201 and a light guide body 203 described later in detail arehoused in the case. On an end surface of the light guide body 203, inorder to convert the divergent light from each of the LED elements 201into substantially parallel light flux as shown in FIG. 2, a lens shapewhose cross-sectional area gradually increases toward a light receivingportion and which functions to gradually reduce a divergence angle bytotal reflection plural times when propagating inside is provided. On anupper surface thereof, the liquid crystal display panel 52 constitutingthe image projection apparatus 48 is attached.

Further, on one side surface (left end surface in the example of FIG. 3)of the case of the light source apparatus 101, the LED (Light EmittingDiode) element 201 which is a semiconductor light source and an LEDboard 202 on which the control circuit thereof is mounted are attached,and a heat sink which is a member for cooling the heat generated by theLED element and the control circuit is attached to an outer surface ofthe LED board 202 in some cases.

On the other hand, on a frame (not shown) of the liquid crystal displaypanel attached to the upper surface of the case of the light sourceapparatus 101, the liquid crystal display panel 52 attached to theframe, an FPC (Flexible Printed Circuits: Flexible Wiring Board) (notshown) electrically connected to the liquid crystal display panel, andthe like are attached. Namely, though described in detail later, theliquid crystal display panel 52 which is a liquid crystal displayelement generates the display image by modulating the intensity oftransmitted light based on the control signal from the control circuit(not shown here) constituting an electronic apparatus together with theLED element 201 which is a solid light source. At this time, since theimage light to be generated has a narrow diffusion angle and includesonly a specific polarization component, a novel and non-conventionalimage display apparatus that is close to a surface-emitting laser imagesource driven by an image signal can be obtained.

At present, a laser light flux having the same size as the imageobtained by the above-mentioned image display apparatus 48 cannot beobtained by using the laser apparatus also from the viewpoint of safety.Therefore, in this embodiment, for example, the light close to theabove-mentioned surface-emitting laser image light is obtained from alight flux from a general light source provided with an LED element.

<Lenticular Lens>

In order to control the diffusion distribution of the image light fromthe liquid crystal display panel 52, the unidirectional emissioncharacteristics (image light in the x-axis direction in the drawing) canbe controlled by optimizing the lens shape by providing a lenticularlens 800 shown in FIG. 5 between the above-mentioned light sourceapparatus 101 and the liquid crystal display panel 52 or on the surfaceof the liquid crystal panel 52. Further, by arranging the microlensarray in a matrix shape, the emission characteristics of the image lightflux from the image projection apparatus 48 can be controlled in thex-axis direction and the y-axis direction, and as a result, an imagedisplay apparatus having desired diffusion characteristics can beobtained.

Subsequently, the configuration of the optical system housed in the caseof the light source apparatus 101 will be described in detail below withreference to FIG. 4 together with FIG. 3 described above.

Since FIG. 3 and FIG. 4 are cross-sectional views, only one of theplurality of LED elements 201 constituting the light source is shown,and these are converted to substantially collimated light by the shapeof alight receiving end surface 203 a of the light guide body 203 asdescribed above. Therefore, the light receiving portion on the endsurface of the light guide body and the LED element are attached so asto keep a predetermined positional relationship.

Each of the light guide bodies 203 is made of a translucent resin suchas acrylic resin. Also, the LED light receiving surface at the end ofthe light guide body has a conical convex outer peripheral surfaceobtained by, for example, rotating a paraboloid cross section, has atthe top thereof a concave portion in which a convex portion (that is, aconvex lens surface) is formed at the center thereof, and has a convexlens surface projecting outward (or a concave lens surface recessedinward) in the central portion of the flat surface portion thereof (notshown). The outer shape of the light receiving portion of the lightguide body to which the LED element 201 is attached has a parabolicshape forming a conical outer peripheral surface, and it is set withinan angular range capable of totally reflecting the light emitted in theperipheral direction from the LED element therein or has a reflectionsurface formed thereon.

On the other hand, the LED element 201 is arranged at a predeterminedposition on the surface of the so-called LED board 202 which is thecircuit board thereof. The LED board 202 is arranged and fixed withrespect to the LED collimator (light receiving end surface 203 a) suchthat the LED element 201 on the surface thereof is located at thecentral portion of the concave portion described above.

With the configuration described above, the light emitted from the LEDelement 201 can be taken out as substantially parallel light by theshape of the light receiving end surface 203 a of the light guide body203 described above, and the utilization efficiency of the generatedlight can be improved.

As described above, the light source apparatus 101 is configured byattaching the light source unit, in which a plurality of LED elements201 as a light source is arranged, on the light receiving end surface203 a serving as a light receiving portion provided on the end surfaceof the light guide body 203. The divergent light flux from the LEDelement 201 is converted to substantially parallel light by the lensshape of the light receiving end surface 203 a on the end surface of thelight guide body, is guided inside the light guide body 203 as indicatedby arrows (horizontal direction in the drawing), and is then emitted tothe liquid crystal display panel 52 arranged approximately parallel tothe light guide body (vertical direction in the drawing) by a light fluxdirection changing unit 204. By optimizing the distribution (density) ofthe light flux direction changing unit 204 by the internal shape or thesurface shape of the light guide body, the uniformity of the light fluxincident on the liquid crystal display panel 52 can be controlled.

FIG. 3 is a cross-sectional layout view for describing the configurationand operation of the light source of the present embodiment to performthe polarization conversion in the light source apparatus 101 includingthe light guide body 203 and the LED element 201 described above. InFIG. 3, the light source apparatus 101 includes the light guide body 203having the light flux direction changing unit 204 provided on itssurface made of plastic or the like or in its inside, the LED element201 as a light source, a reflection sheet 205, a retardation plate 206,the above-mentioned lenticular lens 800, and the like, and the liquidcrystal display panel 52 having a polarization plate provided on a lightsource light incident surface and an image light emission surface isattached on its upper surface as the image projection apparatus 48.

Further, a film or sheet-shaped reflection type polarization plate 49 isprovided on the light source light incident surface (lower surface inthe drawing) of the liquid crystal display panel 52 corresponding to thelight source apparatus 101, by which one polarized wave (for example, Pwave) 212 of the natural light flux 210 emitted from the LED lightsource 201 is selectively reflected, and the reflected light isreflected by the reflection sheet 205 provided on one surface (lowerpart of the drawing) of the light guide body 203 and is directed againtoward the liquid crystal display panel 52.

Then, by providing a retardation plate (λ/4 plate) 206 between thereflection sheet 205 and the light guide body 203 or between the lightguide body 203 and the reflection type polarization plate 49, the lightis reflected by the reflection sheet 205 and is transmitted twice toconvert the reflection light flux from p-polarized light to s-polarizedlight, so that the utilization efficiency of the light source light asthe image light is improved. Since the image light flux whose lightintensity is modulated by the image signal in the liquid crystal displaypanel 52 (arrows 213 in FIG. 3) is incident on the window glass 220 at alarge incident angle as shown in FIG. 1, the reflectance at thetransparent sheet 51 is increased, and favorable diffusioncharacteristics for monitoring inside or outside the store (space) canbe obtained.

FIG. 4 is a cross-sectional layout view for describing the configurationand operation of the light source of the present embodiment to performthe polarization conversion in the light source apparatus 101 includingthe light guide body 203 and the LED element 201 similarly to FIG. 3.The light source apparatus 101 of FIG. 4 also includes the light guidebody 203 having the light flux direction changing unit 204 provided onits surface made of plastic or the like or in its inside, the LEDelement 201 as a light source, the reflection sheet 205, the retardationplate 206, the above-mentioned lenticular lens 800, and the like, andthe liquid crystal display panel 52 having a polarization plate providedon a light source light incident surface and an image light emissionsurface is attached on its upper surface as the image projectionapparatus 48.

Further, the film or sheet-shaped reflection type polarization plate 49is provided on the light source light incident surface (lower surface inthe drawing) of the liquid crystal display panel 52 corresponding to thelight source apparatus 101, by which one polarized wave (for example, Swave) 211 of the natural light flux 210 emitted from the LED lightsource 201 is selectively reflected, and the reflected light isreflected by the reflection sheet 205 provided on one surface (lowerpart of the drawing) of the light guide body 203 and is directed againtoward the liquid crystal display panel 52. By providing a retardationplate (λ/4 plate) between the reflection sheet 205 and the light guidebody 203 or between the light guide body 203 and the reflection typepolarization plate 49, the light is reflected by the reflection sheet205 and is transmitted twice to convert the reflection light flux froms-polarized light to p-polarized light, so that the utilizationefficiency of the light source light as the image light is improved.Even when the image light flux whose light intensity is modulated by theimage signal in the liquid crystal display panel 52 (arrows 214 in FIG.4) is incident on the window glass 220 at a large incident angle asshown in FIG. 1, the reflection on the surface is reduced, and the imagelight can be efficiently diffused to the outside by the transparentsheet 51.

Here, the function of the lenticular lens 800 shown in FIG. 5 will bedescribed. The lenticular lens 800 makes it possible to efficientlyreflect or diffuse the light emitted from the image display apparatus 48described above on the transparent sheet 51 on the window glass 220 byoptimizing the lens shape. Namely, for example, as shown in FIG. 6(a)and FIG. 6(b), by arranging two lenticular lenses in combination ormicrolens array in a matrix shape with respect to the image light fromthe image projection apparatus 48 and providing a sheet for controllingdiffusion characteristics, the luminance (relative luminance) of theimage light can be controlled in accordance with its reflection angle (0degrees in the vertical direction) in the X-axis direction and theY-axis direction.

In this embodiment, by the lenticular lens 800 mentioned above, theluminance characteristics in the vertical direction are made steeper asshown in FIG. 6(b) and further the light luminance (relative luminance)by the reflection and diffusion is increased by changing the balance ofthe directional characteristics in the vertical direction (positive andnegative directions of the y-axis) as compared with the conventionalcase, whereby the image light having a narrow diffusion angle (highstraightness) and including only a specific polarization component likethe image light from the surface-emitting laser image source isobtained, and is efficiently delivered to the eyes of the observer.

Also, by achieving the directional characteristics having significantlynarrower angle in both the x-axis direction and the y-axis directionshown as the first embodiment and the second embodiment by theabove-mentioned light source apparatus, as compared with the diffusioncharacteristics of the emission light (referred to as conventional inFIG. 6) from the general liquid crystal panel shown in FIG. 6(a) andFIG. 6(b), the image display apparatus capable of emitting light of aspecific polarization which emits an image light flux almost parallel toa specific direction can be realized.

FIG. 7 shows an example of the characteristics of the lenticular lensused in this embodiment. In this example, in particular, thecharacteristics in the X direction (vertical direction) are shown, and acharacteristic O shows a luminance characteristic in which the peak inthe light emission direction is at an angle of about 30 degrees upwardfrom the vertical direction (0 degrees) and is vertically symmetrical.Also, characteristics A and B in FIG. 7 further show examples of thecharacteristics in which the image light above the peak luminance iscondensed at around degrees to increase the luminance (relativeluminance). Therefore, in these characteristics A and B, the luminance(relative luminance) of light is sharply reduced at the angle exceeding30 degrees as compared with the characteristic O.

Namely, with the above-mentioned optical system including the lenticularlens, the image light from the image projection apparatus 48 can bereflected and diffused while increasing (emphasizing) the luminancethereof in a specific direction via the transparent sheet 51 on thewindow glass 220 described below. Consequently, the image light from theimage projection apparatus 48 can be efficiently delivered to the eyesof the observer inside or outside the room as the light having a narrowdiffusion angle (high straightness) and including only a specificpolarization component like the image light from the surface-emittinglaser image source. According to this, even if the intensity (luminance)of the image light from the image projection apparatus 48 is reduced,the observer can accurately recognize the image light and obtaininformation. In other words, it is possible to realize the informationdisplay system with lower power consumption by further reducing theoutput of the image projection apparatus 48.

<Light Direction Changing Panel>

FIG. 8 is a schematic explanatory diagram for describing the principleof the light direction changing panel 54 constituting a part of theinformation display system of the present embodiment and provided on theupper surface of the image display apparatus 48 described above. Thelight flux from the light guide body 203 of the light source apparatus101 described above is incident from the incident surface (lower surfacein the drawing) of the light direction changing panel 54, and isrefracted in a desired direction θ3 by the lens function of the linearFresnel lens provided on the emission surface (upper surface in thedrawing). At this time, the desired direction θ3 is uniquely derivedfrom Snell's law by the incident angle θ2 of the light flux to theFresnel lens, the Fresnel angle θ0 of the Fresnel lens, and therefractive index n of the base material.

As a result, the directivity in a desired direction can be given to thesubstantially parallel light flux from the light guide body. Namely, theimage light emitted from the liquid crystal display panel 52constituting the image display apparatus 48, which has high straightnessand includes only a specific polarization component, is directed to thetransparent sheet 51 provided on the window glass 220 described laterwithout being visually recognized by an observer inside or outside thestore (space). Thereafter, the image light is unidirectionally reflectedand diffused by the transparent sheet 51, and the reflected image isvisually recognized by the observer.

Namely, by the light direction changing panel 54, the image light itselffrom the image display apparatus 48 (see FIG. 1) is not visuallyrecognized directly inside the space and thus does not disturb theobserver in the store, and only the reflected image of the reflectedlight will be monitored by the observer. By providing a light-absorbingpaint or pigment on a connecting surface 88 of the Fresnel lens, thegeneration of light other than the light flux traveling in a desireddirection is suppressed. As a result, unnecessary light is not mixedwith the image light reflected by the window glass 220, so that theimaging performance is not impaired.

<Protective Cover>

FIG. 9 is a cross-sectional view showing a schematic configuration of aprotective cover 50 provided on the upper surface of the above-mentionedlight direction changing panel 54. Black stripes 59 are provided on apart of the light emission side of a substantially transparent basematerial 56. In order to reduce the surface reflection of external lightincluding sunlight, a black paint such as a paint containing carbonblack is preferably used as the black stripe 59. Further, by providingan antireflection film for suppressing surface reflection on the portionwhere the black stripe is not provided, the external light reflection onthe surface of the protective cover 50 is significantly reduced, and thehindrance due to the external light reflection is reduced. On the otherhand, in order to enhance the light-shielding performance againstsunlight, it is preferable to make the antireflection film have aproperty of reflecting near-infrared light and infrared light.

On the other hand, on the light incident side (lower side of thedrawing) of the substantially transparent base material 56, a film 50 athat absorbs or reflects the P wave component of the solar light flux isformed or adhered. As a result, since the P wave component of sunlightand the like do not enter the image projection apparatus 48, thereliability regarding light resistance and heat resistance is greatlyimproved. On the other hand, since it also has the characteristics of afilter that selectively transmits the S-polarized image light outputfrom the image projection apparatus 48, the contrast performance of theobtained image is significantly improved.

By the way, in a general TFT (Thin Film Transistor) liquid crystalpanel, luminance and contrast performances differ depending on the lightemission direction due to the mutual characteristics of the liquidcrystal and the polarization plate. In the evaluation under themeasurement environment shown in FIG. 10, the characteristics of theluminance and the viewing angle in the up-down direction of the panelare excellent at the angle slightly deviated (+5 degrees in thisembodiment) from the emission angle vertical to the panel surface(emission angle: 0 degrees) as shown in FIG. 11. This is because thecharacteristics of twisting light in the up-down direction of the liquidcrystal do not become 0 degrees when the applied voltage is maximum.

On the other hand, as shown in FIG. 12, the contrast performance in theup-down direction is excellent in the range of −15 degrees to +15degrees, and the use in the range of ±10 degrees centered on 5 degreescan obtain the best characteristics when combined with the luminancecharacteristics.

Also, as shown in FIG. 13, the characteristics of the luminance and theviewing angle in the left-right direction of the panel are excellent atthe emission angle vertical to the panel surface (emission angle: 0degrees). This is because the characteristics of twisting light in theleft-right direction of the liquid crystal become 0 degrees when theapplied voltage is maximum.

Similarly, as shown in FIG. 14, the contrast performance in theleft-right direction is excellent in the range of −5 degrees to −10degrees, and the use in the range of ±5 degrees centered on −5 degreescan obtain the best characteristics when combined with the luminancecharacteristics. Therefore, by making the light enter the liquid crystalpanel from the direction in which the most excellent characteristics canbe obtained by the light flux direction changing unit 204 provided inthe light guide body 203 of the light source apparatus 101 describedabove and performing the light modulation by the image signal, the imagequality and performance of the image display apparatus 48 can beimproved.

In order to bend the image light from the liquid crystal panel as theimage display element in a desired direction, it is preferable toprovide the light direction changing panel 54 on the emission surface ofthe liquid crystal panel.

<Image Light Control Film>

FIG. 15 is a cross-sectional view of an image light control film 70having a function of restricting the emission direction of the imagelight. The image light control film 70 is provided on, for example, theupper surface of the image display apparatus 48 and emits the imagelight from the liquid crystal display panel 52 in a specific direction(in the direction of the white arrow in the drawing). Also, since ablack portion 70 b of the image light control film 70 blocks a part ofthe light, the light does not directly enter the observer's eyes, and itis thus possible to prevent the hindrance due to the direct light fromthe image display apparatus 48 entering the observer's eyes.

The image light control film 70 has a function of preventing the imagelight from directly directing to the observer, while the image lightpasses through a transparent portion 70 a and is reflected by awindshield 6 or the like and can be recognized by the driver who is theobserver. As the image light control film 70, for example, a viewingangle control film (VCF: View Control Film) of Shin-Etsu Polymer Co.,Ltd. is suitable, and since the structure thereof is such thattransparent silicon and black silicon are alternately arranged and asynthetic resin is arranged on a light incident/emission surface to forma sandwich structure, the same effect as that of the image light controlfilm 70 of the present embodiment can be expected.

It is desirable that a pitch h of the transparent portion 70 a and theblack portion 70 b of the viewing angle control film described above is⅓ or less with respect to the pixels of the image to be displayed. Atthis time, when the viewing angle α is desired to be larger than 90degrees, a thickness W should be set such that h/w becomes larger than1.0, and when the viewing angle α is desired to be smaller than 90degrees, the thickness W should be set such that h/w becomes smallerthan 1.0. On the other hand, there is no practical problem if the haze(HAZE) defined by the ratio of the diffusion transmittance and theparallel light transmittance of the transparent sheet 51 is 10% or less,but it is preferably 4% or less.

<Unidirectional Transparent Sheet: First Example of Reflection Type>

Next, in the overall configuration of the information display systemaccording to the present embodiment, in particular, the configurationand function of the transparent sheet 51 will be described withreference to FIG. 16. Here, the S polarized wave of the sunlightincident on the window glass 220 from an oblique direction is reflected,and the P polarized wave is transmitted and directed to the transparentsheet 51. The transparent sheet 51 is composed of a polarization plate57 that transmits S waves, a transparent diffusion sheet material 55,and a retardation plate 58.

For this transparent sheet 51, a film obtained by melting and stretchinga thermoplastic polymer in which zirconium nanoparticles and diamondnanoparticles having a large refractive index are dispersed, forexample, “KALEIDO SCREEN” manufactured by JXTG Energy Co., Ltd. can beused (see Patent Document 3 mentioned above). Consequently, the displaywhich is transparent and does not prevent the observer from monitoringthe scenery of the outside world (outside the store) when the image isnot displayed and the display which diffuses and reflects the imagelight such that the observer inside or outside the store (space) canvisually recognize the image information when the image is displayed,that is, the unidirectional display can be realized. At this time, thereis no practical problem if the haze (HAZE) defined by the ratio of thediffusion transmittance and the parallel light transmittance of thetransparent sheet 51 is 10% or less, but it is preferably 4% or less.

Since the image light from the image projection apparatus 48 isS-polarized wave, it scatters inside the transparent diffusion sheetmaterial 55 described above and is emitted toward the observer in astate where the reflectance in the oblique incidence is high. On theother hand, a part of the image light whose polarization direction isdisturbed due to the scattering diffuses and transmits through thetransparent diffusion sheet material 55, and is emitted toward thewindow glass 220. Since the difference in refractive index is small onthe incident surface of the window glass 220, the level of the doubleimage generated by the reflected light is low.

On the other hand, since the intensity of the reflected light generatedon the emission surface (the surface in contact with the outside world)of the window glass 220 is mostly the S polarization component, thereflectance is large. Since the image light reflected on this surfacepasses through the polarization plate 57 again after reflection and isthen absorbed, it does not return to the observer side. Therefore, sincethe light intensity of the double image generated by the reflected imageof the window glass 220 can be significantly reduced, the image qualityis greatly improved. Similarly, it goes without saying that the sameeffect can be obtained by attaching the above-mentioned transparentsheet 51 to the combiner instead of the window glass 220 as the imagereflection surface.

With the transparent sheet 51 described above, the sunlight component ofthe P-polarized light that has passed through the window glass 220(passed through also the combiner afterward in the combiner method)under predetermined conditions in the daytime is absorbed in front ofthe information display system and the light direction changing panel 54and the protective cover 50 provided on the upper surface thereof, sothat it is possible to prevent it from returning to the liquid crystaldisplay panel and the polarization plate.

<Unidirectional Transparent Sheet: Second Example of Reflection Type>

The second example of the reflection type unidirectional transparentsheet will be described with reference to FIG. 17. In this example, theimage light control film 70 shown in FIG. 15 is further added on thetransparent sheet 51 described above to form an external light controlfilm (hereinafter, denoted by reference numeral 70).

As described above, the S polarized wave of sunlight incident on thewindow glass 220 from an oblique direction is reflected, and the Ppolarized wave thereof is transmitted and directed to the transparentsheet 51. At this time, it is absorbed by the black region 70 b (shownin gray in FIG. 17) provided in the external light control film 70, anddoes not reach the inside of the room or the vehicle in which the imagedisplay apparatus is arranged.

Further, since it is not mixed with the image light from the imagedisplay apparatus 48, deterioration of the image quality is prevented.The transparent sheet 51 is made of the transparent diffusion sheetmaterial 55. For this transparent sheet 51, a film obtained by meltingand stretching a thermoplastic polymer in which zirconium nanoparticlesand diamond nanoparticles having a large refractive index are dispersed,for example, “KALEIDO SCREEN” manufactured by JXTG Energy Co., Ltd. canbe used (see Patent Document 3 mentioned above). Consequently, thedisplay which is transparent and does not prevent the observer frommonitoring the scenery of the outside world (outside the store) when theimage is not displayed and the display which diffuses and reflects theimage light such that the observer inside or outside the store (space)can visually recognize the image information when the image isdisplayed, that is, the unidirectional display can be realized.

Further, the above-mentioned external light control film 70 does notobstruct the monitoring of the scenery of the outside world because thelight of the outside world passes through the transparent portion 70 awhen the observer monitors the scenery of the outside world. As thisexternal light control film 70, for example, a viewing angle controlfilm (VCF: View Control Film) of Shin-Etsu Polymer Co., Ltd. issuitable, and since the structure thereof is such that transparentsilicon and black silicon are alternately arranged and a synthetic resinis arranged on a light incident/emission surface to form a sandwichstructure, the same effect as that of the external light control film ofthe present embodiment can be expected. It is desirable that a pitch hof the transparent portion 70 a and the black portion 70 b of theviewing angle control film described above is ⅓ or less with respect tothe pixels of the image to be displayed. At this time, when the viewingangle α is desired to be larger than 90 degrees, a thickness W should beset such that h/w becomes larger than 1.0, and when the viewing angle αis desired to be smaller than 90 degrees, the thickness W should be setsuch that h/w becomes smaller than 1.0.

On the other hand, there is no practical problem if the haze (HAZE)defined by the ratio of the diffusion transmittance and the parallellight transmittance of the transparent sheet 51 is 10% or less, but itis preferably 4% or less. In addition, the total transmittance of 75% ormore is required when it is attached to a windshield for use in avehicle.

Since the image light from the image projection apparatus 48 isS-polarized wave, it scatters inside the transparent diffusion sheetmaterial 55 described above and is emitted toward the observer in astate where the reflectance in the oblique incidence is high. On theother hand, a part of the image light whose polarization direction isdisturbed due to the scattering diffuses and transmits through thetransparent diffusion sheet material 55, and is emitted toward thewindow glass 220. Since the difference in refractive index is small onthe incident surface of the window glass 220, the level of the doubleimage generated by the reflected light is low.

On the other hand, since the intensity of the reflected light generatedon the emission surface (the surface in contact with the outside world)of the window glass 220 is mostly the S polarization component, thereflectance is large. Since the image light reflected on this surfacepasses through the external light control film 70 again after reflectionand is then absorbed in the black region 70 b, it does not return to theobserver side. Therefore, since the light intensity of the double imagegenerated by the reflected image of the window glass 220 can besignificantly reduced, the image quality is greatly improved. Similarly,it goes without saying that the same effect can be obtained by attachingthe above-mentioned transparent sheet 51 to the combiner instead of thewindow glass 220 as the image reflection surface.

With the unidirectional transparent sheet 51 described above, thesunlight component of the P-polarized light that has passed through thewindow glass 220 (passed through also the combiner afterward in thecombiner method) under predetermined conditions in the daytime isabsorbed in front of the information display system and the lightdirection changing panel 54 and the protective cover 50 provided on theupper surface thereof, so that it is possible to prevent it fromreturning to the liquid crystal display panel and the polarizationplate.

<Unidirectional Transparent Sheet: First Example of Transmission Type>

FIG. 18 shows a configuration of a transparent sheet 51′ that diffusesthe image light flux to the outside of the vehicle or the outside of theroom. The polarization plate 57 that transmits P waves and theretardation plate 58 are provided on the image light flux incidentsurface of the transparent diffusion sheet material 55, and the imagelight flux reflected by the transparent diffusion sheet material 55 isprevented from returning to the inside of the room (space in which theinformation display apparatus is installed). As a result, the imageprojected on the window glass 220 does not hinder the observer. As theoptimum phase difference of the retardation plate 58 provided betweenthe polarization plate 57 and the transparent diffusion sheet material55, an optimal value is preferably selected in accordance with thediffusion characteristics of the transparent diffusion sheet. When thediffusion angle is large, it is preferably close to λ/4, and when thediffusion angle is small, better conversion performance can be obtainedby combining with a λ/8 plate or the like.

Also, it can be confirmed that, by providing a sheet to which thereflection enhanced coating whose reflectance of a specific polarizedwave is increased is applied instead of the above-mentioned transparentdiffusion sheet material 55 or applying the reflection enhanced coatingto the surface of the polarization plate, the reflectance of the imagelight flux can be increased and simultaneously the intensity of thedouble image generated by the reflected image of the window glass 220can be significantly reduced, that is, it can be confirmed that the sameeffect as the above-mentioned technique can be obtained.

Further, it is preferable that, by using, for example, PDLC (PolymerDispersed Liquid Crystal) of Santech Display Co., Ltd. instead of thetransparent diffusion sheet material 55 described above, the image lightis dispersed without applying a voltage in the image display state andit is used instead of the transparent sheet by turning it to atransparent state by applying a voltage in the image non-display state.Also, the inventors have revealed by the experiment that it is possibleto realize a screen having a novel function capable of controlling thediffusion characteristics by changing the voltage applied to theabove-mentioned PDLC and capable of controlling the transmittance inaccordance with the image by modulating the applied voltage insynchronization with the ON/OFF or the intensity of the image signal.

<Unidirectional Transparent Sheet: Second Example of Transmission Type>

FIG. 19 shows a configuration in which the image light control film 70shown in FIG. 15 is used as the external light control film(hereinafter, denoted by a reference numeral 70) in addition to thetransparent sheet 51′ that diffuses the image light flux to the outsideof the vehicle or the outside of the room. As described above, the Spolarized wave of sunlight incident on the window glass 220 from anoblique direction is reflected, and the P polarized wave thereof istransmitted and directed to the transparent sheet 51. At this time, itis absorbed by the black portion 70 b (shown in gray in FIG. 19)provided in the external light control film 70, and does not reach theinside of the room or the vehicle in which the image display apparatusis arranged. In addition, since it is not mixed with the image lightfrom the image display apparatus 48, deterioration of the image qualityis also prevented. The transparent sheet 51′ is made of the transparentdiffusion sheet material 55.

For this transparent sheet 51′, a film obtained by melting andstretching a thermoplastic polymer in which zirconium nanoparticles anddiamond nanoparticles having a large refractive index are dispersed, forexample, “KALEIDO SCREEN” manufactured by JXTG Energy Co., Ltd. can beused (see Patent Document 3 mentioned above). Consequently, the displaywhich is transparent and does not prevent the observer from monitoringthe scenery of the outside world (outside the store) when the image isnot displayed and the display which diffuses and reflects the imagelight such that the observer outside the store (space) can visuallyrecognize the image information when the image is displayed, that is,the unidirectional display can be realized.

Further, in the above-mentioned external light control film 70, theimage light incident on the window glass 220 from an oblique directionis hardly blocked by the black portion 70 b and passes through thetransparent portion 70 a, and is thus diffused by the transparent sheet51′, which enables the image display to the outside world (to theoutside of the vehicle or outside of the store). As the external lightcontrol film 70, for example, a viewing angle control film (VCF: ViewControl Film) of Shin-Etsu Polymer Co., Ltd. is suitable, and since thestructure thereof is such that transparent silicon and black silicon arealternately arranged and a synthetic resin is arranged on a lightincident/emission surface to form a sandwich structure, the same effectas that of the external light control film of the present embodiment canbe expected.

It is desirable that a pitch h of the transparent portion 70 a and theblack portion 70 b of the viewing angle control film described above is⅓ or less with respect to the pixels of the image to be displayed. Atthis time, when the viewing angle α is desired to be larger than 90degrees, a thickness W should be set such that h/w becomes larger than1.0, and when the viewing angle α is desired to be smaller than 90degrees, the thickness W should be set such that h/w becomes smallerthan 1.0. Also, the energy loss can be reduced by matching aninclination angle γ of the black portion with the incident angle of theimage light determined by the mounting positions of the image displayapparatus 48 and the window glass.

On the other hand, there is no practical problem if the haze (HAZE)defined by the ratio of the diffusion transmittance and the parallellight transmittance of the transparent sheet 51 is 10% or less, but itis preferably 4% or less. Also, it can be confirmed that, by providing asheet to which the reflection enhanced coating whose reflectance of aspecific polarized wave is increased is applied instead of theabove-mentioned transparent diffusion sheet material 55, the reflectanceof the image light flux can be increased and simultaneously theintensity of the double image generated by the reflected image of thewindow glass 220 can be significantly reduced, that is, it can beconfirmed that the same effect as the above-mentioned technique can beobtained.

Further, it is preferable that, by using, for example, PDLC (PolymerDispersed Liquid Crystal) of Santech Display Co., Ltd. instead of thetransparent diffusion sheet material 55 described above, the image lightis dispersed without applying a voltage in the image display state andit is used instead of the transparent sheet by turning it to atransparent state by applying a voltage in the image non-display state.Also, the inventors have revealed by the experiment that it is possibleto realize a screen having a novel function capable of controlling thediffusion characteristics by changing the voltage applied to theabove-mentioned PDLC and capable of controlling the transmittance inaccordance with the image by modulating the applied voltage insynchronization with the ON/OFF or the intensity of the image signal.

Since the image source constituting the image projection apparatus 48described above is a liquid crystal panel, when the observer wearspolarized sunglasses, a problem that a specific polarized wave isblocked and the observer cannot see the image occurs. In order toprevent this, a film 50 a such as a λ/4 plate, a λ/8 plate, or a λ/16plate is arranged between the film 50 a for absorbing or reflecting theP wave component of the solar light flux provided on the light incidentside surface of the protective cover 50 provided on the light emittingside of the image projection apparatus 48 described above and the basematerial 56. By providing the wave plate 50 b, preferably, thepolarization direction of the light flux is aligned in a specificdirection, the image light is made to have the optimum polarizationangle, and the polarization direction of the polarized sunglasses andthe polarization axis are shifted from each other by a desired amount.

On the other hand, even with the same polarization, by rotating theabsorption axis so as to shift the absorption axis of the polarizationplate on the light emission side of the liquid crystal panel by 30degrees or more with respect to the absorption axis of the polarizedsunglasses, the absorption becomes about 50%, so that the problem thatthe image cannot be seen can be solved.

Further, when the polarization axis is rotated to be approximated tocircular polarization, the polarization axis of the image light from theinformation display system is rotated from S-polarized light. Thus,since the reflectance by the window glass 220 is lowered and thebrightness of the image is lowered, the balanced selection therebetweenis preferable.

In the information display system according to the present embodimentdescribed above in detail, since the image light from the imageprojection apparatus 48 has a narrow diffusion angle (high straightness)and includes only a specific polarization component like the image lightfrom the surface-emitting laser image source, various information can bedisplayed inside or outside the space by using, for example, the showwindow 220 that constitutes the space, the utilization efficiency of theshow window can be greatly improved, high-quality images can bedisplayed with high resolution, and power consumption can besignificantly reduced by improving the utilization efficiency of thelight emitted from the light source.

Further, when displaying a larger image, a large-sized liquid crystaldisplay panel 52 obtained by combining a plurality of relativelyinexpensive liquid crystal display panels by making the joints thereofcontinuous may be adopted as the liquid crystal display panel 52 that isan image display element constituting the image projection apparatus 48together with the light source apparatus 101. In this case, by directingthe light flux from the above-mentioned light source apparatus 101 tothe transparent sheet 51 parallelly provided on the window glass 220 andunidirectionally reflecting/diffusing it by the transparent sheet 51,more expanded image information can be displayed while significantlyreducing the power consumption.

In the above description, an example in which the information displaysystem is applied to a store which is a space partitioned by a showwindow which is a transparent member such as glass and information isunidirectionally displayed to the inside or outside thereof by using theshow window 220 has been described, but the present invention is notlimited to this example. Namely, the information display systemaccording to the present invention can unidirectionally display theinformation to the inside or outside of the space by using thetransparent member that partitions the space as long as the space ispartitioned by using a transparent member such as glass, and otherexamples of the information display system will be described below.

<Vehicle Information Display System>

In the information display system according to the above-describedembodiment, (1) the image light generated from the image projectionapparatus 48 and emitted toward the show window 220 which is a member towhich the light is projected (referred to as a projected member) isconverted to image light having a narrow diffusion angle (highstraightness) and including only a specific polarization component likethe image light from the surface-emitting laser image source, so thathigh-quality images can be displayed with high resolution and powerconsumption can be significantly reduced by improving the utilizationefficiency of the emitted light, and (2) the overall outer shape of theapparatus can be formed to be flat (panel-like) shape as is apparentfrom the component parts described above. Therefore, various examples ofthe so-called vehicle information display systems in which theinformation display system according to the above-described embodimentis applied by utilizing these features to a vehicle such as anautomobile, a train, and an aircraft instead of a space such as a storementioned above will be described in detail below.

FIG. 20 shows an example in which a vehicle information display systemis mounted on an ordinary passenger car. In this example, imageinformation is displayed on some or all of a part of the windshield 6(upper part of a steering 43), a rear glass, a part of a side glass 6″(gray part), and the like by the vehicle information display panel 100according to the present embodiment.

As a specific configuration for displaying an image on (a part or allof) the window glass of an automobile, for example, as shown in FIG. 21,the image projection apparatus 48 including a large-sized liquid crystalpanel 52 a (see also reference numeral 52 in FIG. 2) is installed on aceiling portion of a vehicle body 1, and a plurality of light guidebodies 203 a, 203 b, 203 c, 203 d, 203 e, 203 f, and 203 g (see alsoreference numerals 101 and 203 in FIG. 2) constituting the light sourceapparatus 101 is provided on a part of the back surface of the liquidcrystal panel as the light source apparatus 101, so that the image lighteach having a narrow diffusion angle (high straightness) and an alignedpolarization plane like the light from the surface-emitting laser lightsource can be obtained as indicated by the white arrows in the drawing.

These light fluxes are further projected to the windshield 6, the rearglass 6′, and the side glass 6″ serving as projected surfaces of theimage information by the light direction changing panels (not shownhere, see reference numeral 54 in FIG. 2) provided so as to correspondto each of the light guide bodies 203 a to 203 g, and the image isunidirectionally displayed to the inside or outside of the vehicle 1. Atthis time, as shown in FIG. 22, at the positions of the liquid crystalpanels constituting the image projection apparatus 48, the imagescorresponding to them are separately displayed, respectively. Also,since the distances from the image display apparatus to the windowglasses and the shapes of the window glasses are different, the originalimage is distorted such that the projected images are displayed in thecorrect shape. As the resolution of the large-sized liquid crystal panel52 a, about 8 k is sufficient.

Alternatively, as shown in FIG. 23 and FIG. 24, it is also possible todisplay the image to each of the window glasses by installing aplurality of image display apparatuses 48 a, 48 b, 48 c, 48 d, 48 e, and48 f on a ceiling portion of a vehicle body instead of the imageprojection apparatus 48 composed of the large-sized liquid crystal panel52 a described above. Also at this time, since the distances from theimage display apparatuses to the window glasses and the shapes of thewindow glasses are different, the original image is preferably distortedsuch that the projected images are displayed in the correct shape.

In the above, an example in which various images are displayed on theimage display region in which the transparent sheet 51 is attached tothe window glass 6 by the vehicle information display system has beendescribed. However, the present invention is not limited to this, and itcan be confirmed that, by providing the reflection enhanced coatingwhose reflectance of a specific polarized wave is increased instead ofthe above-mentioned transparent diffusion sheet material, thereflectance of the image light flux can be increased and simultaneouslythe intensity of the double image generated by the reflected image ofthe window glass 6 can be significantly reduced, and thus the sameeffect as the above-mentioned technique can be obtained.

FIG. 25 and FIG. 26 are external views showing the case where thevehicle information display system is mounted on a commercial vehiclesuch as a bus or a train. The windshield 6, the rear glass 6′ (notshown), the side glass 6″, and the like (collectively referred to as“shield glass”) as the transparent projected members on which the imagelight is projected and displayed are present in the vehicle body 1. Inparticular, the windshield 6 in front of the driver's seat of thevehicle body 1 has different inclination angles to the vehicle bodydepending on the types of the vehicle. The inventors have studied theradius of curvature thereof in order to realize the optimum virtualimage optical system. As a result, it has been found that the windshield6 of a bus, a railroad vehicle, and the like has the followingrelationship between the radius of curvature Rh in the horizontaldirection horizontal to the ground contact surface of the vehicle andthe radius of curvature Rv in the direction vertical to the horizontalaxis, and the radius of curvature Rh in the horizontal direction isclose to a flat surface in many cases.

Rh>Rv

This vehicle information display system is configured tounidirectionally display the image information to the inside or theoutside of the vehicle by using the windshield 6, the rear window 6′,and/or the side glass 6″ which are the translucent member partitioningthe space in the vehicle and serve as the projected member constitutinga part of the vehicle, and it relates to the system capable ofdisplaying the image information to the driver and the passenger in thevehicle when the driver is driving the own vehicle and capable ofdisplaying the image information also to the outside of the vehicle.Consequently, the driver and the passenger can monitor the necessaryinformation displayed on a display region such as the windshield 6inside the vehicle as appropriate, but the information cannot bemonitored from the outside. Alternatively, the image information can bedisplayed also to the outside of the vehicle via the rear glass 6′ orthe side glass 6″ (and the windshield 6), and this displayed informationcan be monitored from the outside but cannot be monitored from theinside, so that it does not obstruct the monitoring of the outsidescenery by the driver and the passenger and does not hinder the driving.

Further, in the vehicle information display system, since the vehicleitself is exposed to natural light including sunlight, it is necessaryto take some measures for sunlight. However, as shown in FIG. 27,natural light such as sunlight is not only the light of the widewavelength range from the ultraviolet to the infrared but also exists inthe state where the lights of two types of polarization directions suchas the light in the vibration direction perpendicular to the travelingdirection of the light and the light in the horizontal direction(hereinafter, referred to as S-polarized light and P-polarized light)are mixed. In particular, in the region in which the incident angle onthe windshield 6 is larger than 50 degrees, as shown in FIG. 28, thereflectance on the glass surface varies depending on the S-polarizedlight, the P-polarized light, and the incident angle, respectively.

Therefore, in the present embodiment, based on the above-mentionedfindings by the inventors, that is, considering that most of thesunlight entering through the windshield 6 is a P-polarized lightcomponent, it has been confirmed that it is particularly effective toreduce the P wave component in order to suppress external lightincluding sunlight entering the information display apparatus. Inaddition, it has been confirmed that it is effective to use the S wavecomponent as the image light to be emitted from the information displayapparatus and reflected in the vehicle and monitored by the driver andthe passenger serving as the observers.

<First Specific Configuration Example of Vehicle Information DisplaySystem>

Subsequently, another vehicle information display system in which theinformation display system according to the present embodiment isapplied to a vehicle and a specific configuration thereof will bedescribed in detail with reference to FIG. 29 and FIG. 30.

FIG. 29 and FIG. 30 show the overall configuration of the vehicleinformation display system in which the information display systemaccording to the present embodiment is applied to the vehicle and theimage information is displayed in a part of the outside scenerymonitored by the driver via the windshield 6 which is a transparentprojected member constituting a part of the vehicle. Here, thewindshield 6 is divided into a plurality of regions, the image lightfrom the image projection apparatus 48 is diffused and reflected in apart of the regions (in this example, the upper part of the windshield6), and the reflected image is unidirectionally monitored by the driverand the passengers directly. As a result, the driver and the passengercan monitor the necessary information displayed in the display region ofthe windshield 6 as appropriate, but on the other hand, the informationcannot be visually recognized from the outside of the vehicle.

In this vehicle information display system, as shown in FIG. 29, theimage projection apparatus 48 projects the high-resolution mapinformation from the smartphone 300 or the like (image of a large-sizedhigh-resolution image display apparatus) onto the inner surface of thewindshield 6 via the light direction changing panel 54 and theprotective cover 50 (hereinafter, the light source apparatus 101 servingas a backlight apparatus, the image projection apparatus 48, the lightdirection changing panel 54, and the protective cover 50 constitutingthe information display system according to the present embodiment arecollectively referred to as the “information display apparatus” 100)though described later in detail, so that the image is reflected via thetransparent sheet 51 provided on the surface of the windshield 6 to theeyes 8 of the observer (driver), thereby displaying the image on thewindshield 6.

Note that an example of the case of using the smartphone 300 which is ahigh-performance mobile terminal device equipped with a navigationfunction that provides map information and the like is shown here, andthe display screen from the smartphone 300 is input through a wiredconnection terminal or by a wireless connection such as Bluetooth(registered trademark) or Wifi (registered trademark) so as to be ableto display the image thereof, so that the driver can monitor thehigh-resolution image information by using the vehicle informationdisplay system. Although not shown here, it is natural that thesmartphone is provided with a controller composed of a CPU (CentralProcessing Unit) and various solid-state memories such as RAM and ROMfunctioning as work memory and information storage like the imageprojection apparatus 48 described above, and has a function ofgenerating and displaying the necessary image on the display apparatus(liquid crystal display) thereof.

Further, a more specific configuration of the vehicle informationdisplay system will be described. The image display element 52constituting the image projection apparatus 48 of the informationdisplay apparatus 100 is composed of, for example, a relatively largeliquid crystal display panel having a screen size of more than 6 inches.In general, since the radius of curvature of the windshield 6 ispartially different in many cases, non-uniform (longitudinal andlateral) distortions occur in the displayed image depending on the placewhere the image is reflected. Therefore, distortion correction isrequired to obtain a correct image when the reflected image is viewedfrom the monitoring direction. In order to perform correction at a levelthat does not cause a problem in practical use by this distortioncorrection, the resolution of the panel needs to be 1280×720 dots ormore.

Also, the image display apparatus 48 further includes the light sourceapparatus 101 constituting a light source thereof together with theabove-mentioned liquid crystal display panel 52, and the light sourceapparatus 101 is shown above the liquid crystal display panel 52 in FIG.29.

The liquid crystal display panel (element) 52 obtains an illuminationlight flux having strong directivity by the light source apparatus 101which is a backlight apparatus and emits the image light modulated inaccordance with an input image signal to the transparent sheet 51provided on the windshield 6 as shown FIG. 29. Also, in FIG. 29, thevehicle information display system further includes the light directionchanging panel 54 configured to control the directional characteristicsof the light flux 30 emitted from the light source apparatus 101 and anarrow-angle diffusion plate (not shown) as needed together with theimage display apparatus 48 including the light source apparatus 101 andthe liquid crystal display panel 52. Namely, polarization plates areprovided on both surfaces of the liquid crystal display panel 52, andthe image light having a specific polarization is emitted with the lightintensity thereof modulated by the image signal. Consequently, thehigh-resolution image from the smartphone 300 or the like (image oflarge-sized high-resolution image display apparatus) is projected towardthe windshield 6 via the light direction changing panel 54, and it isreflected toward the eyes 8 of the observer (driver) via the transparentsheet 51 provided on the surface thereof.

Note that the image projection apparatus 48 constituting the vehicleinformation display system includes the light source apparatus 101, theliquid crystal display panel 52, and the like as shown in the drawing,and the configuration and operation of the image projection apparatus 48including the light source apparatus 101 have already been describedabove as the embodiment of the image display apparatus and are notdescribed in detail here. However, almost all the light generated by theLED can be taken out as parallel light, and the utilization efficiencyof the generated light can be improved. Further, it is also possible toimprove its uniform illumination characteristics, and at the same time,it is possible to manufacture it in a small size and at low costincluding a modularized light source apparatus of the S-polarized light.

Though not shown here, with the image light having a narrow diffusionangle (high straightness) and including only a specific polarizationcomponent like the image light from the surface-emitting laser imagesource obtained by adopting the lenticular lens or the microlens arraysheet (not shown) whose configurations and characteristics are shown inFIG. 5 to FIG. 7, the image light from the image projection apparatus 48is efficiently delivered to the eyes 8 of the observer inside or outsidethe room, so that it is possible to realize the vehicle informationdisplay system in which the high-quality image can be displayed withhigh resolution and the power consumption can be reduced by reducing theoutput of the image projection apparatus 48.

In addition, the light direction changing panel 54 provided on the lowersurface of the image projection apparatus 48 described above is also thesame as that described above with reference to FIG. 8 and others, andthe configuration and operation thereof are not described in detailhere. However, the image light which is emitted from the liquid displaypanel 52 constituting the image projection apparatus 48 of the vehicleinformation display system is directed to the transparent sheet 51provided on the windshield 6 without being visually recognized by thedriver and the passenger in the vehicle, and then, the image light isunidirectionally reflected and diffused by the transparent sheet 51 andthe reflected image is visually recognized by the driver. Namely, withthis light direction changing panel 54, the image light itself from theimage projection apparatus 48 is not visually recognized directly fromthe inside of the vehicle and thus does not obstruct the driving, andonly the reflected image by the reflected light thereof is monitored bythe driver and the passenger.

Also, the protective cover 50 arranged in contact with the ceilingsurface of the vehicle and provided on the upper surface of the lightdirection changing panel 54 described above is also the same as thatdescribed above with reference to FIG. 9 and others, and theconfiguration and operation thereof are not described in detail here.However, in the vehicle information display system, in particular, thehindrance due to the reflection of external light at the time when thedriver drives the vehicle can be reduced.

In addition, the S-polarized wave of the sunlight incident on thewindshield 6 from an oblique direction is reflected, and the P-polarizedwave thereof is transmitted and directed to the transparent sheet 51. Asdescribed above with reference to FIG. 16 and others, the transparentsheet 51 is composed of the polarization plate 57 that transmits the Swaves and the transparent diffusion sheet material 55, is transparentwhen the image is not displayed, and does not prevent the driver frommonitoring the scenery of the outside world (outside the vehicle). Onthe other hand, the transparent sheet 51 diffuses and reflects the imagelight when the image is displayed, so that the unidirectional display inwhich the driver and the passenger can visually recognize the imageinformation can be realized.

Further, it has already been described that the same effect can beobtained also in the configuration shown in FIG. 17. At this time, thereis no practical problem if the haze (HAZE) defined by the ratio of thediffusion transmittance and the parallel light transmittance of thetransparent sheet 51 is 10% or less, but it is preferably 4% or less.Meanwhile, the HAZE of window glass for automobiles is 2% or less.

On the other hand, since the image light from the image projectionapparatus 48 constituting the vehicle information display system isS-polarized wave, it scatters inside the transparent diffusion sheetmaterial 55 constituting the transparent sheet 51 described above and isemitted toward the observer in a state where the reflectance in theoblique incidence is high. On the other hand, a part of the image lightwhose polarization direction is disturbed due to the scattering diffusesand transmits through the transparent diffusion sheet material 55, andis emitted toward the windshield 6. Since the difference in refractiveindex is small on the incident surface of the windshield 6, the level ofthe double image generated by the reflected light is low.

On the other hand, since the intensity of the reflected light generatedon the emission surface (the surface in contact with the outside world)of the windshield 6 is mostly the S polarization component, thereflectance is large. Since the image light reflected on this surfacepasses through the polarization plate 57 again after reflection and isthen absorbed, it does not return to the observer side. Therefore, sincethe double image caused by the reflected image of the windshield 6 isnot generated, the image quality is greatly improved. Similarly, it goeswithout saying that the same effect can be obtained by attaching theabove-mentioned transparent sheet 51 to the combiner instead of thewindshield 6 as the image reflection surface.

With the transparent sheet 51 described above, as is clear from FIG. 16and FIG. 17, the sunlight component of the P-polarized light that haspassed through the windshield 6 (passed through also the combinerafterward in the combiner method) under predetermined conditions in thedaytime is absorbed in front of the image projection apparatus 48including the light source apparatus 101 and the liquid crystal panel 52constituting the vehicle information display system, the apparatusincluding the light direction changing panel 54, and the protectivecover 50 provided on the upper surface thereof, so that it is possibleto prevent it from returning to the liquid crystal display panel and thepolarization plate.

In the above example, the case in which the reflection type transparentsheet 51 is adopted as the unidirectional transparent sheet 51 providedon the windshield 6 has been described, but also by adopting thetransmission type transparent sheet 51′ described with reference to FIG.18 instead of it, the image light flux can also be diffusedunidirectionally, that is, to the outside of the vehicle. In that case,a polarization plate that transmits P waves and a retardation plate areprovided on the image light flux incident surface of the transparentdiffusion sheet material 55 constituting the transparent sheet 51′, andthe image light flux reflected by the transparent diffusion sheetmaterial 55 is prevented from returning to the inside of the vehicle(the space where the vehicle information display system is installed).As a result, the driving of the driver is not obstructed by the imageprojected on the windshield 6.

As the optimum phase difference of the retardation plate 58 providedbetween the polarization plate 57 and the transparent diffusion sheetmaterial 55, an optimal value is preferably selected in accordance withthe diffusion characteristics of the transparent diffusion sheet. Whenthe diffusion angle is large, it is preferably close to λ/4, and whenthe diffusion angle is small, better conversion characteristics can beobtained by combining with a λ/8 plate or the like. Further, the sameeffect can be obtained also in the second example of the unidirectionaltransparent sheet described with reference to FIG. 19.

In the vehicle information display system including the image projectionapparatus 48 having the light source apparatus 101 and the liquidcrystal display panel 52, the light direction changing panel 54, and thelike described above in detail, as shown by the arrows in FIG. 29, thelarge-sized high resolution image projection apparatus 48 is provided atthe position (ceiling surface) corresponding to the image display regionof the upper region of the windshield 6 which is the transparent memberpartitioning the space inside the vehicle, and the display image thereofis reflected on the windshield, so that the reflected image thereof canbe directly monitored by the driver and the passenger. At that time, ahigh-quality image can be displayed with high resolution by the imagelight having a narrow diffusion angle (high straightness) and includingonly a specific polarization component like the image light from thesurface-emitting laser image source, and power consumption can besignificantly reduced by improving the utilization efficiency of theemitted light.

<Second Specific Configuration Example of Vehicle Information DisplaySystem>

In the above, the vehicle information display system configured todisplay an image by the image projection apparatus 48, the lightdirection changing panel 54, and the like by using the window glassesincluding the windshield 6 and the side glass 6″ partitioning the spacein the vehicle has been described, but the present invention is notlimited to this. For example, an image can be displayed also by using arear glass, or a head-up display (HUD) type information displayapparatus (hereinafter referred to as “HUD apparatus”) can also bemounted and used at the same time, and the example in such a case willbe described below.

Subsequently, FIG. 31 shows an example in which the vehicle informationdisplay system is mounted on an ordinary passenger vehicle whoseappearance is shown in FIG. 30 instead of the above-mentioned largevehicle, and an image is unidirectionally displayed on a part of thewindshield 6 (upper part of the steering 43) and a part of the sideglass 6″ to the inside or outside of the vehicle by an image displayapparatus 704 and a light source apparatus 710 of the HUD apparatus 700provided instead of the image projection apparatus 48 and the lightdirection changing panel 54 described above.

Here, as the HUD apparatus, a known general apparatus can be adopted,and the outline thereof will be schematically described below as anexample.

FIG. 31 is a schematic configuration diagram showing the HUD apparatus700 including its peripheral device configuration. Here, in order toform a virtual image V1 in front of the own vehicle in the line of sight(eye point) of the driver 8, various information reflected by theprojected member 6 (inner surface of the windshield) is diffused andreflected by the transparent sheet 51 provided on the windshield 6 tothe inside of the vehicle and is displayed as a real image.

The above-mentioned HUD apparatus 700 includes the image displayapparatus 704 that corresponds to the image projection apparatus 48described above and generates the image light of the information to bedisplayed and the light source apparatus 710 that corresponds to thelight source apparatus 101 described above and supplies the light to theimage display apparatus 704. In order to control the diffusiondistribution of the image light from the image display apparatus 704,the unidirectional control can be achieved by optimizing the lens shapeby providing a lenticular lens on a part of the surface of the imagedisplay apparatus 704 in the same manner as above.

Further, the image light flux from the HUD apparatus 700 is emitted froman opening (not shown) toward the windshield 6. Namely, by adopting theimage light having a narrow diffusion angle (high straightness) andincluding only a specific polarization component like the image lightfrom the surface-emitting laser image source obtained by adopting thelenticular lens or the microlens array sheet described above in the HUDapparatus 700 constituting the vehicle information display system, theimage light can be efficiently delivered to the eyes 8 of the observerinside or outside the room, and as a result, the vehicle informationdisplay system capable of displaying the high-quality image with highresolution and reducing the power consumption by reducing the output ofthe HUD apparatus 700 can be realized.

In addition, the HUD apparatus 700 includes a controller 740 thatcontrols the backlight thereof. The image display apparatus 704 and theoptical components including the backlight reflect and diffuse thedisplay image of the image display apparatus 704 on the transparentsheet 51 attached to the windshield 6, thereby directing it toward thedriver's line of sight 8. As the image display apparatus 704, forexample, an LCD (Liquid Crystal Display) having a backlight can bepresented.

The controller 740 in the drawing constituting the HUD apparatusacquires, from a navigation system 761, various information such as thespeed limit and the number of lanes of the road corresponding to thecurrent position where the vehicle is traveling, the planned route ofthe own vehicle set in the navigation system 761, and others asforeground information (that is, information displayed in front of theown vehicle by the above-mentioned virtual image).

Also, a driving support ECU 762 is a controller for realizing drivingsupport control by controlling the drive system and the control systemin accordance with the obstacle detected as a result of the monitoringby a peripheral monitoring device 763. Such driving support controlincludes well-known techniques such as cruise control, adaptive cruisecontrol, pre-crash safety, and lane keeping assist. The peripheralmonitoring device 763 in the drawing is configured to monitor thesituation around the own vehicle, and is, for example, a camera thatdetects an object existing in the vicinity of the own vehicle based onan image taken around the own vehicle, a searching device that detectsan object existing around the own vehicle based on the result oftransmitting and receiving searching waves, and the like.

The controller 740 of the HUD apparatus described above acquiresinformation from the driving support ECU 762 (for example, the distanceto the preceding vehicle, the orientation of the preceding vehicle, theposition where an obstacle or a sign exists, etc.) as foregroundinformation. Further, an ignition (IG) signal and own vehicle stateinformation are input to the controller 740. The own vehicle stateinformation thereof is information acquired as vehicle information anddoes not require high-resolution display, and includes, for example,warning information indicating that the predetermined abnormal conditionhas occurred such as the remaining amount of fuel of the internalcombustion engine and the temperature of cooling water.

It also includes the operation result of the direction indicator, thetraveling speed of the own vehicle, the shift position information, andthe like. The controller 740 described above is activated when anignition signal is input. Further, the projected member 6 may be anymember such as a combiner on which information can be projected otherthan the windshield described above, and any member can be adopted aslong as the real image can be formed in front of the own vehicle in thedriver's line of sight 8 so as to be visually recognized by the driver.

Subsequently, FIG. 32 shows an example of the arrangement in the cockpitof the automobile in which the above-mentioned image projectionapparatus 48, the transparent sheet 51, and/or the HUD apparatus 700 aremounted. FIG. 32 (a) shows the arrangement of the system correspondingto the automobile having the steering arranged on the left side, andFIG. 32 (b) shows the arrangement of the system corresponding to theautomobile having the steering arranged on the right side.

In an HUD image display region (1 a) of FIG. 32, the image informationis reflected and displayed on the windshield 6 by using the HUDapparatus 700 shown above. Also, in an image display region (lb)(corresponding to a region where the transparent sheet 51 is attached),image information is reflected on the windshield 6 by using theapparatus (here, “vehicle information display apparatus” denoted byreference numeral 100) including the image projection apparatus 48having the light source apparatus 101 and the liquid crystal displaypanel 52 and the light direction changing panel 54, and the reflectedimage thereof is monitored by the driver. At that time, as shown in thedrawing, it is preferable that the image display region (lb) is set inthe upper part of the windshield 6 and the HUD image display region (1a) is set in a range or region which does not obstruct the monitoring ofthe scenery outside the vehicle for the driver, for example, in therange where the bonnet of the own vehicle is monitored.

As shown in FIG. 32, the vehicle information display apparatus 100described above is arranged on the ceiling surface of the vehicle, whilethe HUD apparatus 700 is arranged inside the dashboard 47 between thewindshield 6 and the steering 43 so as to be directed toward thesteering 43 at the position continuous to the windshield 6. As a result,it is possible to provide the vehicle information display system, inwhich when the driver drives his/her own vehicle, the image of thelarge-sized high resolution image display apparatus is reflected on thewindshield 6 by the vehicle information display apparatus 100 and thereflected image thereof can be monitored by the driver or the passengeron the outside scenery monitored through the windshield 6, that is, in apart of the region of the windshield 6 or the information from the HUDapparatus 700 can also be displayed as needed.

Namely, in the image display region (lb) in which the transparent sheet51 is attached to the windshield 6, the image light from the vehicleinformation display apparatus 100 is reflected and monitored by thedriver. At that time, the augmented reality can be realized in a pseudomanner by, for example, superimposing the image display region (lb) onthe scenery monitored by the driver while driving. The image projectedat this time is preferably set in a range or region that does notobstruct the monitoring of the scenery outside the vehicle for thedriver.

For example, by providing a camera 72 configured to monitor the state ofthe driver and the state in the vehicle on a rear-view mirror 71 shownin FIG. 32, it is also possible to control the emission direction of theimage light from the vehicle information display apparatus 100 so as tobe matched with the height of eyes of the driver.

<Modification of Vehicle Information Display System: Display to Outside>

According to the embodiment described above in detailed, when the driverdrives his/her own vehicle, the necessary image information can beunidirectionally displayed with high resolution so as to be monitored bythe driver and the passenger in the vehicle via the windshield 6 as theprojected member which is the shield glass constituting the vehicle.

At that time, the information cannot be monitored from the outside ofthe vehicle. However, the vehicle information display system accordingto the present invention is not limited to the above-describedembodiment, and it is also possible to display the image information tothe outside of the vehicle. Namely, the image information can bedisplayed to the inside or the outside of the vehicle not only via thewindshield 6 described above but also via the rear glass 6′ and the sideglass 6′ which are shield glasses in the same manner as above.

For example, in the system of this embodiment, it is possible to displayinformation indicating the state of a vehicle such as “vacant” on a partof the windshield 6 of a taxi and further on the rear glass 6′ or theside glass 6″. Alternatively, it is also possible to display otherinformation such as promotion and advertisement to the outside of thevehicle. Also, in a vehicle such as a bus or a train, information suchas the route and the destination can be unidirectionally displayed onthe windshield, the rear glass, the side glass, and others to theoutside of the vehicle. The configuration of the vehicle informationdisplay system when displaying information to the outside will bedescribed below.

FIG. 33 shows a system in which necessary image information isunidirectionally displayed with high resolution to the outside of thevehicle via the windshield 6 as a projected member so as to be monitoredfrom the outside. More specifically, an example of displaying the stateof a taxi (such as “vacant”) on the windshield of a taxi is shown here.In this example, in the configuration shown in FIG. 32, the image lightfrom the vehicle information display apparatus 100′ is diffused andtransmitted on transparent sheet 51′ (see FIG. 18) provided on thesurface of the windshield 6, and the image thereof is transmitted anddisplayed to the outside of the vehicle as indicated by arrows in FIG.18 and the like such that a pedestrian or the like can monitor it. As aresult, although the driver or the passenger can display the necessaryinformation on the windshield 6 in a relatively large size to theoutside of the vehicle, the display does not obstruct the monitoring ofthe scenery outside the vehicle to be monitored from the inside of thevehicle and does not hinder the driving of the driver.

Further, by providing a reflection enhanced coating whose reflectance ofa specific polarized wave is increased instead of the above-mentionedtransparent diffusion sheet material 55 of the transparent sheet 51′,the reflectance of the image light flux can be increased andsimultaneously the intensity of the double image generated by thereflected image of the windshield 6 can be significantly reduced.Namely, it can be confirmed that the same effect as the above-mentionedtechnique can be obtained.

Further, it is preferable that, by using, for example, PDLC (PolymerDispersed Liquid Crystal) of Santech Display Co., Ltd. instead of theabove-mentioned transparent diffusion sheet material 55 of thetransparent sheet 51′, the image light is dispersed without applying avoltage in the image display state and it is used instead of thetransparent sheet by turning it to a transparent state by applying avoltage in the image non-display state.

Similarly to the above, the transparent sheet 51′ is composed of thepolarization plate 57 that transmits S waves and the transparentdiffusion sheet material 55, and by using a film obtained by melting andstretching a thermoplastic polymer in which zirconium nanoparticles anddiamond nanoparticles having a large refractive index are dispersed, forexample, “KALEIDO SCREEN” manufactured by JXTG Energy Co., Ltd. (seePatent Document 2), it is transparent when the image is not displayedand it diffuses and transmits the image light when the image isdisplayed. Consequently, the image information can be displayed to theoutside in the state where the image information is not visuallyrecognized by driver and the passenger and the monitoring of the outsidescenery is not obstructed.

The function of the transparent sheet 51′ in this case will bedescribed. The transparent sheet 51′ is composed of the polarizationplate 57, the transparent diffusion sheet material 55, and theretardation plate 58, and reduces the illuminance of the sunlightincident from an oblique direction by reflecting the S polarized wave ofthereof and transmitting the P polarized wave thereof similarly to theabove. At this time, apart of the sunlight is absorbed by thepolarization plate by rotating the polarization axis of P-polarizedlight by the retardation plate 58. As a result, the damage that theimage projection apparatus 48 receives due to the sunlight can bedispersed.

On the other hand, the image light diffused to the outside of thevehicle by the function of the transparent diffusion sheet material 55(see FIG. 18) is reflected by the rear glass 6′ or the like and returnsto the inside of the vehicle. This light obstructs the driver's field ofview and thus hinders the driving. Therefore, in this embodiment, theretardation plate 58 is arranged between the rear glass 6′ and the likeand the polarization plate 57 to absorb the reflected light by thepolarization plate, so that the information by the image light isunidirectionally displayed to the outside of the vehicle without beingvisually recognized by the driver and the passenger in the vehicle.

Needless to say, the same effect can be obtained also in the secondexample of the unidirectional transparent sheet shown in FIG. 19. Atthat time, the information by the image light does not obstructs themonitoring of the outside scenery by the driver or the passenger in thevehicle and does not hinder the driving. There is no practical problemif the haze (HAZE) defined by the ratio of the diffusion transmittanceand the parallel light transmittance of the transparent sheet 51mentioned above is 10% or less, but it is preferably 4% or less.Meanwhile, the HAZE of window glass for automobiles is 2% or less.

As described above, the display of information to the outside of thevehicle by using a part of shield glasses such as the windshield 6, therear glass, and the side glass would be particularly suitable fordisplaying the above-mentioned information such as “vacant” indicatingthe vacant state of the taxi to pedestrians on the street. Further, asdescribed above, the vehicle information display system according to thepresent embodiment not only unidirectionally displays image informationon the windshield, but also can display various information includingpromotion, advertisement, and notification even in a large vehicle suchas a bus or a train by using the projected member such as the rear glass6′ and the side glass 6″ (see FIG. 25, FIG. 26, and others) which arethe shield glasses constituting the vehicle. In the following, theconfiguration and operation of the vehicle information display system inthe case of displaying information to the outside of the vehicle will bedescribed below.

FIG. 34 shows an example in which information is displayed to, forexample, a pedestrian or the like outside the vehicle via the rear glass6′ constituting a part of the vehicle serving as the projected member.As a result, the driver and the passenger can monitor the necessaryinformation on the windshield 6 described above (see FIG. 25 and thelike), and at the same time, information can be displayed also to theoutside of the vehicle by the rear glass 6′. Note that the driver andthe passenger cannot monitor the information displayed to the outside,and thus, the driver's field of view is not obstructed. Namely, thedisplay of information to the outside of the vehicle does not obstructthe monitoring of the outside scenery by the driver and the passengerinside the vehicle.

In this example, the vehicle information display apparatus 100′ isarranged above the rear glass 6′ which is the projected memberconstituting a part of the vehicle, and the image information isdisplayed by projecting the image light thereof to the image displayregion (1 e) set on the entire surface or a part of the surface of therear glass 6′.

Also in this example, it is natural that the transparent sheet 51′ shownin FIG. 18 and FIG. 19 described above is provided in the image displayregion of the rear glass 6′. In addition, the projected member thatunidirectionally displays the image information to the outside of thevehicle is not limited to the windshield 6 and the rear glass 6′described above, and the side glass 6″ that constitutes the side surfaceof the vehicle (see FIG. 25, FIG. 26, FIG. 31, etc.) can also be used.In this case, though not shown here, it is natural that the vehicleinformation display apparatus 100′ is arranged on a member in thevicinity of the side glass 6″ (for example, a part of adjacent ceilingsurface or window frame) and the transparent sheet 51′ shown in FIG. 18and FIG. 19 described above is provided in the image display region (1d) of the side glass 6″.

The display of the information on the side glass 6″ may be suitable fordisplaying a message such as “Thank you for waiting” or “Please board”in, for example, a taxi to the passenger or the like on the street.

In addition, in the above example, the image vehicle information displayapparatuses 100 and 100′ in which the information is unidirectionallydisplayed to the inside or the outside of the vehicle via the windshield6, the rear glass 6′, and the side glass 6″ which are the projectedmembers constituting the vehicle have been described. However, thepresent invention is not limited to these, and for example, the vehicleinformation display apparatus 100 that displays information to theinside of the vehicle and the vehicle information display apparatus 100′that displays information to the outside of the vehicle can be combinedas appropriate.

According to this, for example, when applied to public transportationsuch as a bus and a train, various types of information includingpromotion, advertisement, notification, and others can be displayed tothe public outside the vehicle via the rear glass 6′ and the side glass6′ (in this case, it is possible to control the display so as not to bevisually recognized from the inside of vehicle), and information can beeffectively displayed to the public. Further, as described above, it isalso possible to simultaneously mount and use the head-up display (HUD)700 as the vehicle information display apparatus.

Further, by using, for example, PDLC (Polymer Dispersed Liquid Crystal)of Santech Display Co., Ltd. instead of the transparent diffusion sheetmaterial 55 described above to form a film that absorbs or reflects thespecific polarized wave on the image light incident side, the imagelight can be displayed to the inside and the outside of the vehicle byturning it to a white state without applying a voltage in the imagedisplay state. It is preferable that it is used instead of thetransparent sheet by turning it to a transparent state by applying avoltage in the image non-display state. When the driver needs to see therear scenery, for example, when a shift lever is shifted to a back gearor it is confirmed by a driver surveillance camera that the point ofview has been moved to a side mirror or a rear-view mirror, the rearvisibility is ensured by applying a voltage to a part of the PDLC tomake the entire surface or a part of the PDLC transparent. The return ofthe image light to the driver side is reduced by the sheet or the filmmentioned above, thereby preventing the hindrance of the driving.

Further, it is also possible to display the image from the HUD apparatus700 described above on the window glass 6 by using the display apparatusincluding the image projection apparatus 48 and the light directionchanging panel 54 described above, and FIG. 29 and FIG. 31 show anexample thereof. The configuration and operation of the HUD apparatus700 are the same as above, and the configuration and operation of thevehicle information display apparatus 100 are also the same as above.Also in this case, similarly to the above, it is possible to improve theutilization efficiency of the generated light and to improve the uniformillumination characteristics, and at the same time, it is possible tomanufacture it in a small size and at low cost including a modularizedlight source apparatus of the S-polarized wave.

In addition, when displaying a larger image via the windshield 6, therear glass 6′ and the side glass 6′ which are projected membersconstituting the vehicle, a large-sized liquid crystal display panel 52obtained by combining a plurality of relatively inexpensive liquidcrystal display panels by making the joints thereof continuous may beadopted as the image display element 52 that constitutes the imageprojection apparatus 48 together with the light source apparatus 101 inthe vehicle information display apparatuses 100 and 100′. In this case,by emitting the light flux from the above-mentioned light sourceapparatus 101 to the transparent sheet 51 parallelly provided on thewindow glass 6 and unidirectionally reflecting and diffusing it by thetransparent sheet 51, the vehicle information display system capable ofdisplaying more expanded image information can be realized relativelyeasily and at low cost while significantly reducing the powerconsumption.

In the vehicle image display system of the HUD apparatus type accordingto the present invention described above, when the image light from theimage display apparatus 48 is parallel and the distance from the windowglass to the eyes 8 of the observer is 80 cm, the relative size of thereflected image (virtual image) shown on the window glass in the casewhere the screen horizontal size of the image display apparatus 48 is 10to 20 inches is obtained by calculation using the distance at which thevirtual image can be seen (position reflected on the window glass) as aparameter. FIG. 35 shows the result thereof.

When a virtual image is formed above an axis L-L′ horizontal to the eyesof the observer, the virtual image appears in the air, and the observercauses motion sickness when the car fluctuates up and down. Therefore,the virtual image should be displayed on or below the horizontal lineL-L′, and the experiments by the inventors have revealed that an angle βformed between the virtual image and the horizontal axis is preferablyin the range of 0 to 8 degrees, and is more preferably in the range of 0to 4 degrees when realizing augmented reality. The virtual imagedistance when β is 4 degrees is 20 m, and the virtual image obtained bythe reflection on the window is about 250 inches when the horizontalsize of the image display apparatus is 10 inches and it is about 500inches when it is 20 inches.

Further, FIG. 36 is a cross-sectional view showing an example in whichthe image display apparatus 48 provided with the above-mentioned imagelight control film 70 (see FIG. 15) having the function of restrictingthe emission direction of the image light is mounted in an automobile.In FIG. 36, similarly to FIG. 3 and FIG. 4 above, the light sourceapparatus 101 includes, for example, the light guide body 203 having thelight flux direction changing unit 204 provided on its surface made ofplastic or the like or in its inside, the LED element 201 as a lightsource, the reflection sheet 205, the retardation plate 206, and thelike, and the liquid crystal display panel 52 having the polarizationplate 49 provided on alight source light incident surface and an imagelight emission surface is attached on its upper surface as the imageprojection apparatus 48 and the image light control film 70 shown inFIG. 15 is provided on its uppermost portion. Since the image light fromthe liquid crystal panel 52 is emitted to a specific direction (towardwindshield 6 in the drawing) and a part of the light is blocked by theblack portion 70 b, the light does not directly enter the eyes of theobserver and the direct light from the image display apparatus 48 doesnot hinder the driving.

The image light control film 70 has a function of preventing the imagelight from directly directing to the observer, while the image lightpasses through the transparent portion 70 a and is reflected by thewindshield 6, so that the driver who is the observer can recognize it.As the image light control film 70, for example, a viewing angle controlfilm (VCF: View Control Film) of Shin-Etsu Polymer Co., Ltd. issuitable, and since the structure thereof is such that transparentsilicon and black silicon are alternately arranged and a synthetic resinis arranged on a light incident/emission surface to form a sandwichstructure, the same effect as that of the image light control film 70 ofthe present embodiment can be expected.

It is desirable that a pitch h of the transparent portion 70 a and theblack portion 70 b of the viewing angle control film described above is⅓ or less with respect to the pixels of the image to be displayed. Atthis time, when the viewing angle α is desired to be larger than 90degrees, a thickness W should be set such that h/w becomes larger than1.0, and when the viewing angle α is desired to be smaller than 90degrees, the thickness W should be set such that h/w becomes smallerthan 1.0. On the other hand, there is no practical problem if the haze(HAZE) defined by the ratio of the diffusion transmittance and theparallel light transmittance of the transparent sheet 51 is 10% or less,but it is preferably 4% or less.

In the foregoing, the various embodiments have been described above.However, the present invention is not limited to the above-describedembodiments, and includes various modifications. For example, the aboveembodiments have described the entire system in detail in order to makethe present invention easily understood, and the present invention isnot necessarily limited to those having all the describedconfigurations. Also, a part of the configuration of one embodiment maybe replaced with the configuration of another embodiment, and theconfiguration of one embodiment may be added to the configuration ofanother embodiment. Furthermore, another configuration may be added to apart of the configuration of each embodiment, and a part of theconfiguration of each embodiment may be eliminated or replaced withanother configuration.

REFERENCE SIGNS LIST

1 . . . automobile (vehicle) body, 6 . . . windshield, 6′ . . . rearglass, 6″ . . . side glass, 100 . . . vehicle information displayapparatus, 101 . . . light source apparatus, 48 . . . image projectionapparatus, 49 . . . reflection type polarization plate, 52 . . . liquidcrystal display panel (element), 50 . . . protective cover, 51 . . .unidirectional transparent sheet, 54 . . . light direction changingpanel, 55 . . . transparent diffusion sheet material, 57 . . .polarization plate, 58 . . . retardation plate, 70 a . . . transparentportion, 70 b . . . black portion, 202 . . . LED board, 203 . . . lightguide body, 205 . . . reflection sheet, 220 . . . show window (windowglass), 300 . . . smartphone

1. An information display system configured to unidirectionally displayan image via a transparent projected member constituting a space toinside or outside of the space, comprising: an image projectionapparatus arranged inside the space and configured to generate andproject image light by modulating a light flux from a light source; atransparent sheet provided on an inner surface of a display regionprovided on a part of the projected member; and a light directionchanging unit configured to direct a direction of the image light fromthe image projection apparatus toward the transparent sheet of thedisplay region, wherein the image projection apparatus includes an imagelight characteristic converting unit for converting the image light fromthe light source constituting the image projection apparatus into imagelight having a narrow diffusion angle and composed of a specificpolarization component.
 2. The information display system according toclaim 1, wherein the image light characteristic converting unit of theimage projection apparatus includes a lenticular lens and a polarizationplate that control a diffusion distribution of the image light.
 3. Theinformation display system according to claim 1, wherein the lightdirection changing unit is formed of a linear Fresnel lens.
 4. Theinformation display system according to claim 1, wherein the space ispartitioned by the transparent projected member and the space is astore.
 5. The information display system according to claim 1, whereinthe image projection apparatus is composed of a single liquid crystaldisplay panel or a plurality of liquid crystal display panels combinedwith each other.
 6. The information display system according to claim 1,wherein the transparent sheet includes a retardation plate, anabsorption type polarization plate that absorbs a specific polarizedwave, and a transparent diffusion sheet material having a lightdiffusion function, and projects the image light whose direction hasbeen changed by the light direction changing unit to the inside or theoutside of the space.
 7. The information display system according toclaim 1, wherein the light source constituting the image projectionapparatus changes a divergent light source that emits natural light to asurface light source by a light guide body and converts the divergentlight source into a substantially parallel light flux by a shape of anend surface of the light guide body, thereby entering it to the imagelight characteristic converting unit.
 8. A vehicle information displaysystem configured to display information to inside or outside of avehicle by using a part of a transparent projected member constitutingthe vehicle as a display region, comprising: an image projectionapparatus provided inside the vehicle and configured to modulate a lightflux from a light source and project image light of the information; atransparent sheet provided on an inner surface of the display region seton a part of the projected member; and a light direction changing unitconfigured to change a direction of the image light from the imageprojection apparatus to the transparent sheet, wherein the imageprojection apparatus includes an image light characteristic convertingunit for converting the image light from the light source constitutingthe image projection apparatus into image light having a narrowdiffusion angle and composed of a specific polarization component. 9.The vehicle information display system according to claim 8, wherein theimage light characteristic converting unit of the image projectionapparatus includes a lenticular lens and a polarization plate thatcontrol a diffusion distribution of the image light.
 10. The vehicleinformation display system according to claim 8, wherein the lightdirection changing unit is formed of a linear Fresnel lens.
 11. Thevehicle information display system according to claim 8, wherein theimage projection apparatus configured to project the image light isattached to a ceiling portion of the vehicle.
 12. The vehicleinformation display system according to claim 8, wherein the imageprojection apparatus is composed of a single liquid crystal displaypanel or a plurality of liquid crystal display panels combined with eachother.
 13. The vehicle information display system according to claim 8,wherein the transparent sheet includes a retardation plate, anabsorption type polarization plate that absorbs a specific polarizedwave, and a transparent diffusion sheet material having a lightdiffusion function, and wherein the image light whose direction has beenchanged by the light direction changing unit is projected to the insideor the outside of the vehicle.
 14. The vehicle information displaysystem according to claim 8, further comprising: a protective coverprovided on one surface of the light direction changing unit andconfigured to reduce a surface reflection of an external light.
 15. Thevehicle information display system according to claim 13, wherein thetransparent sheet reflects the image light whose direction has beenchanged by the light direction changing unit, thereby projecting theimage light to the inside of the vehicle.
 16. The vehicle informationdisplay system according to claim 13, wherein the transparent sheettransmits the image light whose direction has been changed by the lightdirection changing unit, thereby projecting the image light to theoutside of the vehicle.
 17. The vehicle information display systemaccording to claim 14, wherein the protective cover is provided with apolarization film that absorbs or reflects a polarization component fromthe outside of the vehicle.
 18. The vehicle information display systemaccording to claim 8, wherein the projected member is a windshield. 19.The vehicle information display system according to claim 18, wherein aplurality of vehicle information display systems is used so as toproject the image light on the windshield to the inside and the outsideof the vehicle.
 20. The vehicle information display system according toclaim 18 including a head-up display apparatus mounted therein.
 21. Thevehicle information display system according to claim 8, wherein theprojected member is a rear glass or a side glass.
 22. The vehicleinformation display system according to claim 21, wherein one or morevehicle information display systems are used to project the image lighton the rear glass or the side glass to the outside of the vehicle. 23.The vehicle information display system according to claim 8, wherein theimage projection apparatus is composed of a plurality of liquid crystaldisplay panels combined with each other.
 24. The vehicle informationdisplay system according to claim 8, wherein the light sourceconstituting the image projection apparatus changes a divergent lightsource that emits natural light to a surface light source by a lightguide body and converts the divergent light source into a substantiallyparallel light flux by a shape of an end surface of the light guidebody, thereby entering it to the image light characteristic convertingunit.